Prediction of bubble size distributions in large-scale bubble columns using computational fluid dynamics

A precise estimation of bubble size distributions is of fundamental and practical importance to understand the fluid dynamics and to estimate the mass transfer in bubble columns. Multiphase computational fluid dynamic simulations, in the Eulerian multi-fluid framework, are able to predict the local bubble size distributions from the fluid flow conditions by using coalescence and breakage kernels. In particular, this study concerns the prediction of the bubble size distributions in the “pseudo-homogeneous” flow regime, which is characterized by a wide spectrum of bubble sizes and is generally observed in industrial applications. Reliable predictions of the “pseudo-homogeneous” flow regime are, however, limited up to now: one important drawback concerns the selection of appropriate models for the coalescence and break-up. A set of closure relations was collected at the Helmholtz-Zentrum Dresden-Rossendorf that represents the best available knowledge and may serve as a baseline model for further investigations. In this paper, the validation of this set of closure relations has been further extended to the “pseudo-homogeneous” flow regime by comparing experimental and numerical bubble size distributions at different axial positions in a large-diameter and large-scale bubble column. The results have been critically analysed and may serve as basis to improve the coalescence and break-up closures.